Also kept getting the 'site is down for maintenance' message so I checked their facebook page and the links all go to:

http://www.daz3d.com/shop/shop

Which works for me. I don't know if they changed the address or something but my old shortcuts do not work.

On Google, the first result that comes up (an ad) works, while the next one listed as 'DAZ3D Home' does not. The individual sub-links (Shop, Forum, Products, etc) all work, however.